If you're working with a language that has closures, I started to have a heuristic:

  // if you are writing a comment like this
  // explaining what the next block of code does
  // chances are you should just refactor it
  // into a closure
  _doWhateverCommentSaid(arg1, arg2, arg3);

it's true that this needlessly adds stack overhead, but this way, you are more likely to structure your code properly, re-use it properly (which more than pays for the stack overhead), and move your closure / method to be more and more global as needed.

Perhaps if you have a comment like this:

  f(x); // x matches some assumption

then in fact, you should add validation to f itself, in the form of a function, same as above.

  function f(x) {
     _theAssumption(x);
  }

this habit encourages re-use and proper structuring of code.

in short, comments may be an anti-pattern!